Conventionally, there has been a rotating angle detector for detecting the rotating position of a rotor as shown in FIG. 4. FIG. 4 is a perspective view showing the structure of the rotating angle detector. In FIG. 4, 1 denotes a rotor, 2 denotes a permanent magnet, 3 denotes a stator, and 4 denotes a magnetic sensor. The permanent magnet 2 is fixed to the rotor 1 and the magnetic sensor 4 is provided on the stator 3 in a peripheral portion thereof to be opposed to the permanent magnet 2 through a gap. The permanent magnet 2 is magnetized in one direction perpendicularly to an axial direction as shown in an arrow by using a linear magnetic anisotropic magnet. The magnetic sensor 4 is provided in such a manner that each difference in mechanical phase angle is set to be 90 degrees. As a result, it is possible to obtain a sine wave and a cosine wave every rotation of the rotor 1. In the case in which the differential signals of the sine wave and the cosine wave are required, four magnetic sensors 41, 42, 43, and 44 are provided around the permanent magnet 2 to carry out a detection.
Referring to the detecting method of the magnetic sensor, description will be given to an example in which a hall unit is used. FIG. 5 is an explanatory view showing the detection principle of the magnetic one. The hall sensor is formed by a compound semiconductor such as GaAs, InSb or InAs, and output terminals 5a and 5b and input current terminals 6a and 6b are attached to a magnetic sensing section having a thickness d. An input current IC is caused to flow to the input current terminals 6a and 6b so that a potential difference VH between the output terminals 5a and 5b is changed corresponding to a variation of magnetic flux B in magnetic sensors. In the structure shown in FIG. 4, four magnetic sensors are provided. Therefore, a wiring shown in FIG. 6 is obtained. FIG. 6 is a typical diagram showing the wiring in the structure of FIG. 4. In FIG. 6, 51 denotes a magnetic sensor terminal, 61 denotes an input current terminal and 10 denotes a rotation detector. Four wirings are required for each magnetic sensor and 16 signal lines in total are connected. A rotating angle can be detected by calculating a signal sent from the magnetic sensor by means of an angle calculator which is not shown. Referring to a calculating method, a rotating angle θ can be calculated as θ=arctan(Va/Vb), wherein a differential voltage output of two outputs having a diagonal relationship in the four magnetic sensor outputs is represented by Va and a differential voltage output of other magnetic sensors is represented by Vb, for example.
In the conventional art, however, 16 signal lines are required for a rotation detector unit. In the case in which a plurality of rotating angle detectors such as articulated robots are used at the same time or are small-sized, particularly, a friction in a motion is caused so that there is a problem in that a working efficiency is reduced.